1. Field of the Invention
The present invention relates to an exhaust gas muffler particularly useful for two-stroke engines with succeeding catalyst and comprising a double-walled casing having an inlet end receiving a stream of the exhaust gas and an outlet end for the exhaust gas, the outlet end comprising an outer tube surrounding a perforated inner tube spaced therefrom, and the casing including an outer wall and an inner wall defining a gap with the outer wall. A heat-resistant intermediate layer is arranged in the gap between the inner and outer walls, transverse partitions divide the casing into a plurality of chambers between the inlet and outlet ends, and tubes connect the chambers and reverse the exhaust gas stream at least twice between the inlet and outlet ends.
2. Description of the Prior Art
An exhaust gas muffler of this type has been disclosed in U.S. Pat. No. 3,289,786. The outlet communicates directly with the ambient atmosphere and the perforation resonator chamber between the inner and outer outlet tubes is incapable of balancing all unfavorable sound frequencies. The inner wall of the casing is smooth so that heat stresses may occur. As disclosed in col. 14 of the patent (see also U. S. Pat. No. 2,761,525 mentioned there), an intermediate heat-resistant layer of asbestos sheet may be disposed in the double-wall of the casing to reduce the formation of condensation by increasing the temperature inside the muffler casing. This cannot improve the surface sound reflection.